Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.34 (lipoprotein lipase)
7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activity of lipoprotein lipase in the vascular bed represents the major pathway by which triglyceride fatty acid is cleared from the plasma and made available to the epripheral tissues. Recent studies on the properties of the enzyme, both solubilized and membrane-bound have provided new information on the regulation of its activity with the major triglyceride-rich lipoprotein substrates. A key role for this enzyme in the regulation of plasma triglyceride levels is indicated from studies of lipase levels in human adipose tissue and in blood plasma obtained after injection of heparin.
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PMID:Lipoprotein lipase. 19 70

Kinetic analysis of activation of lipoprotein lipase by apo C-2 indicates that the lipase co-protein increase the rate of lipolysis by adsorption to enzyme at the lipid interface, with formation of a 1:1 molar complex, whose dissociation constant in the presence of triglyceride substrate is about 3 X 10(-13) moles cm-3. Activation by apo C-2, like that by the entire lipoprotein apoprotein moiety (Fielding and Fielding, 1976) is reversible by inorganic salts and the dependence of activation on medium ion-pair activity supports the concept that such inhibition is mediated through a single specific anion-binding site of the lipase co-protein.
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PMID:The activation of lipoprotein lipase by lipase co-protein (apo C-2). 19 8

In 18 patients with anorexia nervosa, plasma cholesterol and triglyceride concentral concentrations were repeatedly determined over a period of 14 mo. In 11 patients elevated cholesterol concentrations were found which were due to an increase of low-density lipoprotein cholesterol, whereas high-density lipoprotein and very low density lipoprotein cholesterol levels were in the normal range. The elevated cholesterol values did not correlate with clinical and laboratory parameters such as the degree of weight loss and thyroid function tests. In follow-up studies it could be shown that in patients who regained their original weight, elevated plasma cholesterol concentrations fell to normal levels parallel to weight increase. In patients who showed no change in weight, however, cholesterol levels remained high. The cause for this secondary type II hyperlipoproteinemia in anorexia nervosa is not known. Hepatic triglyceride lipase and lipoprotein lipase activities in post-heparin plasma were found to be low despite normal triglyceride concentrations.
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PMID:Secondary type II hyperlipoproteinemia in patients with anorexia nervosa. 20 20

To identify cells developing into adipocytes by accumulation of triglyceride, rat epididymal fat pad cells from small rats were exposed to (3)H-labeled chylomicron fatty acids in vivo and then liberated with collagenase. Tissue remnants were removed by filtration and mature fat cells by flotation. Aggregating cells were then removed by filtration through a 25- micro m nylon screen. Further purification of cells labeled in vivo was obtained by removing floating cells from those adhering to the bottom of a culture dish. The adhering cells multiplied to a confluent monolayer when cultured in Medium 199 containing serum, glucose, insulin, and a triglyceride emulsion. The cells then gradually enlarged due to granulation of the cytoplasm by a lipid-staining material. After about 2 weeks these granules had coalesced forming mature adipocytes of typical signet-ring appearance. Free adipocytes could then be recovered from the cultures by collagenase treatment. After about 2 weeks of culture these cells had the same size (about 30 micro m) as adipocytes recovered in the original collagenase preparation of the rat epididymal fat pad. They contained triglyceride lipase activity and incorporated glucose into triglycerides to the same extent as cells developed in vivo but had higher lipoprotein lipase activity. In vitro, heparin in a low concentration, prostaglandin E(1), isobutylmethylxanthine, and cholera toxin markedly promoted the development of these cells into adipocytes. This could be shown to occur almost completely indicating that this fraction of cells was homogeneous and consisted of cells with the capacity to form adipocytes. The duplication time was about 2 days and did not change with subculturing. Preadipocytes could be obtained by density gradient centrifugation, isolating triglyceride-containing cells either directly from the pad or after 3 days in culture. All of these cells developed into adipocytes as described above but did not multiply as readily. It was concluded that cells from the epididymal fat pad from small rats can be isolated in a homogenous fraction that develops in culture into cells of identical morphology and function as adipocytes formed in vivo. The differentiation of these cells into adipocytes may be manipulated in vitro.
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PMID:Isolation and characterization of cells from rat adipose tissue developing into adipocytes. 20 38

Hepatic lipase activity and lipoprotein lipase activity were studied in postheparin plasma from 14 patients with various liver disorders. Plasma lecithin: cholesterol acyltransferase (LCAT) activity and lipoprotein composition and structure were also estimated. Five patients had lower hepatic lipase activity than the lowest control value, and in three of these no hepatic lipase activity was detected. Lipoprotein lipase was low in 5 patients, but in only one of them was hepatic lipase activity also low. Hepatic lipase was not significantly correlated to the concentration of plasma triglycerides, either in controls or in patients, whereas lipoprotein lipase was negatively correlated with plasma triglycerides both in controls and patients. Lipoprotein lipase and LCAT activity, but not hepatic lipase, was negatively correlated to the triglyceride content of the low density lipoproteins (density 1.019-1.063 g/ml) from the patients. No specific lipid or lipoprotein pattern was found in plasma from the patients with a low or without any hepatic lipase activity. The results suggest an important role of lipoprotein lipase and LCAT, for the increased content of triglycerides in the low density lipoproteins in patients with liver disease. The role of hepatic lipase remains unclear.
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PMID:Triglyceride lipase activity in postheparin plasma and plasma lipoproteins in liver disease. 20 7

The influence of purified human apolipoprotein C-II on phospholipase A1 and triglyceridase activities of lipoprotein lipase were compared. Lipoprotein lipase was obtained from rat hearts by perfusion with a medium containing heparin and purified on a heparin Sepharose 4-B column. Using phosphatidyl-ethanolamine-coated triglyceride particles as substrate it was found that the phospholipase A1 and triglyceridase activities of lipoprotein lipase similarly depend on the presence of apolipoprotein C-II. Apolipoprotein C-III cannot replace apolipoprotein C-II. However, addition of apolipoprotein C-III in the presence of C-II affects both lipase activities. While strong inhibition of triglyceridase activity was observed under these conditions, phospholipase A1 activity was slightly stimulated. On the basis of these findings a model was constructed for the role of apolipoprotein C-II in lipoprotein lipase action.
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PMID:Triglyceridase and phospholipase A1 activities of rat-heart lipoprotein lipase. Influence of apolipoproteins C-II and C-III. 21 Aug 32

Plasma lipoproteins and postheparin plasma were investigated in a patient with familial LCAT deficiency with normal renal function and without proteinuria. As revealed by gelfiltration the large molecular weight LDL2 was not present, and myelin structures were not found in LDL1 or LDL2 when she was on her ordinary diet. After 60--65% fat diet for one week the large molecular LDL2 was found, but only in low concentration. We have no explanation for the difference in the lipoprotein abnormalities of this patient and others with this disease. There is no major difference in the fat content in the ordinary diet of the Norwegian patients with familial LCAT deficiency, nor has our patient any clinical signs of malabsorption. Furthermore, there was no difference in lipoprotein lipase or hepatic lipase activity in postheparin plasma between our patient and others with the same disease. However, whereas hepatic lipase activity was within the reference values, lipoprotein lipase activity was rather low in all patients investigated. We suggest that impaired VLDL catabolism in plasma, because of LCAT deficiency and low lipoprotein lipase activity, may partly explain the low HDL concentration consistently found in patients with familial LCAT deficiency.
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PMID:Familial lecithin:cholesterol acyltransferase deficiency. Further studies on plasma lipoproteins and plasma postheparin lipase activity of a patient with normal renal function. 21 75

Changes in whole plasma and lipoprotien apoprotein concentrations were determined after a single injection of Triton WR 1339 into rats. Concentrations of apoproteins A-I (an activator of lecithin:cholesterol acyl transferase), arginine-rich apoprotein (ARP), and B apoprotein were measured by electroimmunoassay. The content of C-II apoprotein (an activaor of lipoprotein lipase) was estimated by the ability of plasma and lipoprotein fractions to promote hydrolysis of triglyceride in the presence of cow's milk lipase and also by isoelectric focusing on polyacrylamide gels. Apoproteins C-II and A-I were rapidly removed from high density lipoprotein (HDL) after Triton treatment and were recovered in the d 1.21 g/ml infranate fraction. A-I was then totally cleared from the plasma within 10--20 hr after injection. Arginine-rich apoprotein was removed from HDL and also partially cleared from the plasma. The rise in very low density lipoprotein (vldl) apoprotein that followed the removal of apoproteins from HDL was mostly antributed to the B apoprotein, although corresponding smaller increases were observed in VLDL ARP and C apoproteins. The triglyceride:cholesterol, triglyceride:protein, and B:C apoprotein ratios of VLDL more closely resembled nascent rather than plasma VLDL 10 hr after Triton injection. These studies suggest that the detergent may achieve its hyperlipidemic effct by disrupting HDL and thus removing the A-I and C-II proteins from a normal activating environment compirsing VLDL, HDL, and the enzymes. The possible involvement of intact HDL in VLDL catabolism is discussed in relation to other recent reports which also suggest that abnormalities of the VLDL-LDL system may be due to the absence of normal HDL.
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PMID:Changes in the concentration of plasma lipoproteins and apoproteins following the administration of Triton WR 1339 to rats. 22 Mar 61

The anomalous finding that very low density lipoprotein levels are relatively normal in patients with familial hyperchylomicronaemia has never been satisfactorily explained, particularly in view of the marked reduction or absence of peripheral lipoprotein lipase activity characteristic of this condition. I propose that the discrepancy between the plasma levels of the two triglyceride-rich lipoprotein fractions in these patients is due to the secretion by the liver of triglyceride in the form of chylomicron-like particles, rather than as very low density lipoprotein. The proposed "switch" in the spectrum of lipoproteins secreted by the liver is probably contingent upon the activity of the hepatic lipase present on the liver cell plasma membrane.
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PMID:Why very low density lipoprotein levels are normal in familial hyperchylomicronaemia. 22 32

In contrast to plasma from most other animals, guinea pig plasma causes little or no stimulation of lipoprotein lipase activity. Very low density lipoproteins (VLDL) isolated by ultracentrifugation of guinea pig serum caused a definite stimulation of lipase activity, whereas the infranatant inhibited the activity. Gel filtration in 5 M guanidinium hydrochloride of delipidated VLDL demonstrated that the activation was caused by a low molecular weight protein. The VLDL themselves were hydrolized at similar rates as human VLDL both by guinea pig and by bovine lipoprotein lipases. Thus, guinea pig VLDL contain an activator for lipoprotein lipase analogous to that in other animals and there is enough of the activator to support rapid hydrolysis of the VLDL lipids by the lipase.
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PMID:Guinea pig very low density lipoproteins are a good substrate for lipoprotein lipase. 22 10


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